The factors influencing chondrogenesis are under study. Particular attention is being directed towards the extracellular matrix of developing cartilage and its relationship to normal cellular function. The cartilage system has certain advantages for study in this laboratory since it contains a unique type of collagen and proteoglycan which can be utilized as phenotypic markers, and the expertise and technique are available here to extend these studies to the level of transcriptional or translational control. In these investigations, use is being made of limb mesenchyme cell cultures, mature chondrocytes in cultures, cartilage-producing tumors, and cartilage from various animal mutants which may serve as models for human chondrodystrophies.